Sound-absorbing shielding element

ABSTRACT

A sound-absorbing shielding element, in particular for fitting into a motor vehicle, comprises a layered construction which has a support plate, an acoustically effective porous absorber layer and at least one acoustically effective first microperforated sheet which is arranged on a first side of the absorber layer. An acoustically effective second microperforated sheet is arranged on the first side of the absorber layer.

CROSSREFERENCE TO RELATED APPLICATION

This application claims priority from German patent application 10 2010 051 583.3 filed on Nov. 5, 2010. The entire contents of these priority application are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention relates to sound-absorbing shielding elements. More specifically the invention relates to sound-absorbing shielding elements for fitting into a motor vehicle. Such shielding elements generally have a layered construction.

A sound-absorbing shielding element according to the invention is used in particular in a motor vehicle in order at least to reduce the propagation of sound, which is caused by a source of sound, for example by the exhaust systems in the engine compartment, into the passenger compartment. Various elements which are acoustically effective, i.e. act as sound absorbers, are known. For example, sound absorbers consisting of porous materials, such as foams or nonwoven materials, are known. Furthermore, it is also known that microperforated sheets, for example microperforated aluminium foils, are acoustically effective and can serve as sound absorbers.

Microperforated sheets of this type have a very small thickness in the submillimetre range and have a perforation with holes, the individual diameters of which likewise lie in the submillimetre range, and which have a hole area ratio of less than 10% or even less than 1%. In this case, the hole area ratio is understood as meaning the ratio of the entire area of the holes in a surface region with respect to the area of this surface region of the sheet.

Sound-absorbing shielding elements which consist of a combination of porous materials, such as foams or nonwoven materials, and microperforated sheets, are also known, such as those known from DE 10 2004 050 649 A1.

According to one exemplary embodiment, the sound-absorbing shielding element known from DE 10 2004 050 649 A1 has, in the following order: a support plate, a microperforated sheet, an acoustically effective porous absorber layer and a further microperforated sheet.

This known sound-absorbing shielding element is intended, firstly, to be effective as a heat shield, in order to shield the passenger compartment from the heat arising in the engine compartment, and, secondly, is intended to have sound-absorbing properties, wherein the shielding element is intended to be able to optimally absorb sound over a broad acoustic frequency band.

However, it has been shown in practice that specifically the sound-absorbing properties of said known sound-absorbing shielding element are not optimum over wide acoustic frequency ranges.

SUMMARY OF THE INVENTION

The invention is therefore based on the object of further improving a sound-absorbing shielding element in respect of the sound-absorbing properties thereof.

According to an aspect, a sound-absorbing shielding element is provided, comprising a layered construction having a support plate, an acoustically effective porous absorber layer having a first side and a second side opposite the first side, an acoustically effective first microperforated sheet arranged on the first side of the absorber layer, an acoustically effective second microperforated sheet arranged on the first side of the absorber layer.

Thus, in the sound-absorbing shielding element, the layered construction is selected in such a manner that at least two microperforated sheets are arranged on at least one side of the absorber layer, i.e. on that side of the absorber layer which faces the support plate and/or on that side of the absorber layer which faces away from the support plate. It has turned out in this case that, by means of the arrangement of at least two microperforated sheets on one and the same side of the porous absorber layer, the sound-absorbing properties of the shielding element are significantly improved in relation to the known shielding element which has only one microperforated sheet on both sides of the absorber layer.

In the shielding element according to the invention, the support plate can preferably be provided with a macroperforation with holes which have a diameter of several millimetres, for example approximately 5 mm.

The porous absorber layer of the sound-absorbing shielding element according to the invention can be, for example, a fibrous material or a sponge-like foam, in particular a melamine foam. The thickness of the porous absorber layer can be matched to the need and the particular requirements of the fitting situation in a motor vehicle.

The two abovementioned microperforated sheets which are arranged on the same side of the absorber layer can be microperforated sheets such as are already known for sound absorption purposes.

In a preferred refinement, the first microperforated sheet and the second microperforated sheet are immediately adjacent.

In this refinement, the two microperforated sheets rest directly on each other without one or more further layers being arranged therebetween. This arrangement has proven particularly effectively acoustically with regard to the sound absorption in the sound-absorbing shielding element according to the invention.

It is likewise furthermore preferred if the arrangement consisting of the first microperforated sheet and second microperforated sheet is immediately adjacent to the absorber layer.

In this refinement, the sequence of layers, as seen from the absorber layer, is therefore: porous absorber layer—second microperforated sheet—first microperforated sheet. This refinement has proven particularly advantageous in conjunction with the previously mentioned refinement with regard to the sound-absorbing properties of the sound-absorbing shielding element according to the invention.

An even further improvement of the sound-absorbing properties of the sound-absorbing shielding element according to the invention can be achieved in that a third microperforated sheet is arranged on the second side of the absorber layer, which side faces away from the first side of the absorber layer.

In this refinement, the sound-absorbing shielding element according to the invention therefore has at least three microperforated sheets, of which two are arranged on one side of the absorber layer and the at least one third is arranged on the other side of the absorber layer. Within the context of the invention, it is, of course, possible for at least two microperforated sheets to be arranged on both sides of the absorber layer.

In a further preferred refinement, the first side of the absorber layer is that side of the absorber layer which faces away from the support plate.

This refinement is advantageous in particular if, in the fitting situation of the sound-absorbing shielding element, the support plate is arranged facing the source of sound, for example the exhaust system in the engine compartment of the motor vehicle.

In conjunction with the previously mentioned refinement, the following sequence of layers of the layered construction of the sound-absorbing shielding element according to the invention is preferred: the support plate, optionally the third microperforated layer, the absorber layer, the second microperforated sheet and the first microperforated sheet.

In this context, it is furthermore preferred if the first microperforated sheet, which forms the top sheet, is a heat sealing sheet.

“Sealing sheet” means that the second microperforated sheet can be joined to the support plate, for example in the edge region, by hot adhesive bonding or hot melt adhesive bonding.

The second microperforated sheet and, if present, the third microperforated sheet are preferably also a heat sealing sheet.

In an alternative to the refinement of the at least two microperforated sheets being arranged on that side of the absorber layer which faces away from the support plate, it is also possible for the first side of the absorber layer to be that side of the absorber layer which faces the support plate, and therefore the at least two microperforated sheets are arranged on that side of the absorber layer which faces the support plate.

In a further preferred refinement, the first microperforated sheet and/or the second microperforated sheet and/or optionally the third mircroperforated sheet has a thickness within a range of approximately 20 μm to approximately 150 μm, preferably within a range of approximately 20 μm to approximately 100 μm, furthermore preferably within a range of approximately 20 μm to approximately 80 μm, and furthermore preferably within a range of approximately 40 μm to approximately 60 μm.

In a preferred refinement, the first microperforated sheet and the second microperforated sheet and also the third microperforated sheet each have a thickness of approximately 50 μm.

It goes without saying that the thicknesses of the first microperforated sheet, of the second microperforated sheet and optionally of the third microperforated sheet can be identical to one another but may also vary from sheet to sheet within the stated ranges.

In further preferred refinements, the first microperforated sheet and/or the second microperforated sheet has a perforation with holes which have an individual diameter within a range of approximately 50 μm to approximately 200 μm, preferably within a range of approximately 50 μm to approximately 150 μm, furthermore preferably within a range of approximately 60 μm to approximately 120 μm, and furthermore preferably within a range of approximately 80 μm to approximately 100 μm.

It goes without saying that the holes do not inevitably have to be circular, and therefore individual diameter is understood as meaning the largest dimension of the holes.

In a preferred refinement, the first microperforated sheet and/or the second microperforated sheet each have/has a perforation with holes which have an individual diameter of 90 μm.

It furthermore goes without saying that the individual diameters of the holes in the perforations in the sheets may be identical or different within the same sheet and/or may be identical or different from the first microperforated sheet to the second microperforated sheet.

In another preferred refinement in conjunction with the refinement of the third microperforated sheet being provided, the latter has a perforation with holes which have an individual diameter within the range of approximately 50 μm to approximately 200 μm, preferably within the range of approximately 50 μm to approximately 150 μm, furthermore preferably within the range of approximately 60 μm to approximately 140 μm, and furthermore preferably within the range of approximately 80 μm to approximately 130 μm.

In a preferred refinement, the third microperforated sheet has a perforation with holes which have an individual diameter of 110 μm.

With regard to the hole area ratio, it is preferred in the first microperforated sheet and/or the second microperforated sheet and/or optionally the third microperforated sheet if the respective holes have a surface covering within a range of approximately 20 to approximately 80 holes per cm², preferably within a range of approximately 30 to approximately 70 holes per cm², and furthermore preferably within a range of approximately 40 to approximately 60 holes per cm².

In a preferred refinement, the surface covering of the holes in all three abovementioned microperforated sheets is 52 holes per cm².

It goes without saying that the surface covering of the holes may be different among the sheets.

The microperforated sheets provided in the sound-absorbing shielding element according to the invention are preferably manufactured from aluminium.

According to another aspect, a sound-absorbing shielding element is provided, comprising a layered construction having a support plate, an acoustically effective porous absorber layer, an acoustically effective first microperforated sheet arranged on the first side of the absorber layer, an acoustically effective second microperforated sheet arranged between the absorber layer and the first microperforated sheet, and an acoustically effectice third microperforated sheet arranged between the support plate and the absorber layer.

The second microperforated sheet preferably is immediately adjacent to the first microperforated sheet and to the absorber layer.

The first microperforated sheet preferably is a heat sealing sheet made of aluminium.

Further features and advantages emerge from the description below and the attached drawing.

It goes without saying that the features mentioned above and those which have yet to be explained below can be used not only in the respectively stated combination but also in different combinations or on their own without departing from the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the invention is illustrated in the drawing and is described in more detail hereinbelow with reference thereto. In the drawing:

FIG. 1 shows an exemplary embodiment of a sound-absorbing shielding element in an arrangement between a source of sound and a motor vehicle body part, wherein the individual layers of the layered construction of the shielding element are illustrated in section and, for the sake of clarity, separately from one another; and

FIG. 2 shows an edge region of the shielding element, wherein the individual layers of the sound-shielding element are illustrated in an assembly with one another.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1 and 2 illustrate a sound-absorbing shielding element provided with the general reference number 10. FIG. 1 shows the shielding element 10 in a central region, and FIG. 2 shows the shielding element 10 in an edge region.

The shielding element 10 is preferably used in a motor vehicle. In a motor vehicle, the shielding element 10 serves to prevent sound which is produced by a source of sound 12, for example the exhaust system in the engine compartment of the motor vehicle, from propagating into a passenger compartment 14 of the motor vehicle, or to at least greatly damp the sound produced by the source of sound 12. The shielding element 10 is correspondingly arranged between the source of sound 12 and a body part 16 to which the passenger compartment 14 is connected.

The shielding element 10 has a layered construction which has a support plate 18, an acoustically effective porous absorber layer 20, a first microperforated sheet 22, a second microperforated sheet 24 and a third microperforated sheet 26.

In the exemplary embodiment shown, the shielding element 10 consists exclusively of the abovementioned components 18, 20, 22, 24 and 26.

In the shown fitted position of the shielding element 10, the support plate 18 faces the source of sound 12, and the second microperforated sheet 24 faces away from the source of sound 12.

The first microperforated sheet 22 and the second microperforated sheet 24 are arranged on a first side 28 of the absorber layer 20, wherein the first side 28 faces away from the support plate 18. The first microperforated sheet 22 and the second microperforated sheet 24 are directly adjacent to each other (also see FIG. 2), and the arrangement consisting of the first microperforated sheet 22 and the second microperforated sheet 24, for its part, is directly adjacent to the absorber layer 20.

The third microperforated sheet 26 is arranged on a second side 30 of the absorber layer 20, wherein the second side 30 faces the support plate 18. The third microperforated sheet 26 is directly adjacent both to the absorber layer 20 and to the support plate 18.

In an alternative refinement, it is also possible for the second microperforated sheet 24 to be arranged between the third microperforated sheet 26 and the absorber layer 20 such that two microperforated sheets are arranged on the second side 30 of the absorber layer 20.

It is likewise conceivable for the third microperforated sheet 26 to be omitted, and therefore two microperforated sheets are arranged only on the side 28 of the absorber layer 20.

The support plate 18 is manufactured from metal and has a thickness D₁ of a few mm or approximately 1 mm. The support plate may be provided with knobs in the edge region 18 a while the support plate 18 may be embossed in the region in which it overlaps with the absorber layer 20.

The support plate 18 has a macroperforation with holes 32 which have an individual diameter D₂ of approximately 5 mm.

The support plate 18 can be manufactured in particular from aluminium.

The absorber layer 20 is constructed from a porous material, for example from a sponge-like foam. The absorber layer 20 can be manufactured in particular from melamine foam. The absorber layer 20 has a thickness D₃ which can be within the range of several mm, for example approximately 5 mm. The absorber layer 20 may also be manufactured from a fibrous material, for example a nonwoven, wherein the choice of material and the thickness D₃ of the absorber layer 20 are selected in accordance with the requirements of the fitting situation.

The first microperforated sheet 22 is manufactured from a metal sheet, for example aluminium foil. The first microperforated sheet 22 has a thickness D₄ which lies within a range of approximately 20 μm to approximately 150 μm, preferably within a range of approximately 20 μm to approximately 100 μm, furthermore preferably within a range of approximately 20 μm to approximately 80 μm, and furthermore preferably within a range of approximately 40 μm to approximately 60 μm.

The first microperforated sheet 22 has a perforation with holes 34 which have an individual diameter D₅ within the range of approximately 50 μm to 200 μm, preferably within a range of approximately 50 μm to approximately 150 μm, furthermore preferably within a range of approximately 60 μm to approximately 120 μm, and furthermore preferably within a range of approximately 80 μm to approximately 100 μm.

The holes 34 in the microperforated sheet 22 may be circular or may have a shape differing therefrom.

In a practical application, the first microperforated sheet 22 has a thickness D₄ of 50 μm, and the holes 34 have an individual diameter of 90 μm.

The microperforation of the first microperforated sheet 22 has a surface covering of the holes within a range of approximately 20 to approximately 80 holes per cm², preferably within a range of approximately 30 to approximately 70 holes per cm², and furthermore preferably within a range of approximately 40 to approximately 60 holes per cm².

In a practical application, the surface covering of the holes 34 in the perforation in the microperforated sheet 22 is 52 holes per cm².

The second microperforated sheet 24 has a perforation with holes 36, and the third microporated sheet 26 has a perforation with holes 38.

The thickness D₆ of the second microperforated sheet 24 lies within the abovementioned parameter ranges for the thickness D₄ of the microperforated sheet 22. The thickness D₆ may be identical to the thickness D₄ or differ therefrom.

The thickness D₇ of the third microperforated sheet 26 likewise lies within the abovementioned parameter ranges for the thickness D₄.

In a practical application, the thickness D₆ is 50 μm, and the thickness D₇ is likewise 50 μm.

The holes 36 in the perforation in the second microperforated sheet 24 have an individual diameter which lies within the abovementioned parameter ranges of the individual diameters of the holes 34 in the perforation in the first microperforated sheet 22.

The surface covering of the holes 36 in the perforation in the second microperforated sheet 24 likewise lies within the abovementioned parameter ranges for the surface covering of the holes 34 in the perforation of the first microperforated sheet 22.

In a practical application, the individual diameter of the holes 36 in the perforation in the second microperforated sheet 24 is 90 μm with a surface covering of 52 holes per cm².

The surface covering and the individual diameters of the holes 36 in the perforation in the second microperforated sheet 24 may be identical to or differ from the corresponding sizes of the holes 34 in the perforation in the first microperforated sheet 22.

The holes 38 in the perforation in the third microperforated sheet 26 have an individual diameter within a range of approximately 50 μm to approximately 200 μm, preferably within a range of approximately 50 μm to approximately 150 μm, furthermore preferably within a range of approximately 60 μm to approximately 140 μm, and furthermore preferably within a range of approximately 80 μm to approximately 130 μm.

In a practical application, the holes 38 have an individual diameter of 110 μm.

However, it is also possible for the holes 38 to have the same individual diameters as the holes 34 and/or the holes 36.

The surface covering of the holes 38 lies within the above-mentioned parameter ranges for the surface covering of the holes 34 in the perforation in the first microperforated sheet 22.

In a practical application, the surface covering of the holes 38 is 52 holes per cm².

As illustrated in FIG. 2, the absorber layer 20 and the first microperforated sheet 22 do not extend into the edge region 18 a of the support plate 18.

The support plate 18 preferably has the holes 32 only in the overlapping region with the absorber layer 20.

The first microperforated sheet 22, which forms the top sheet in the layered construction of the shielding element 10, is a heat sealing sheet which is adhesively bonded to the support plate 18 in the edge region 18 a by means of a metal hot melt adhesive. For this purpose, the outer edge 18 b of the support plate 18 is crimped around the end 22 a of the first microperforated sheet 22.

The second microperforated sheet 24 and/or the third microperforated sheet 26 are likewise heat sealing sheets, if the need arises, when an intimate assembly of the components of the shielding 10 is expedient.

The third microperforated sheet 26 is mounted with the edge 26 a thereof between the second microperforated sheet 24 and the support plate 18.

The sound-absorbing shielding element 10 according to the previously described exemplary embodiment has particularly good sound absorption properties over the relevant frequency range of the sound caused by the source of sound 12, specifically owing to the fact that there are two microperforated sheets, such as here the first microperforated sheet 22 and the second microperforated sheet 24, on at least one side of the absorber layer 20. 

1. A sound-absorbing shielding element, comprising a layered construction having: a support plate, an acoustically effective porous absorber layer having a first side and a second side opposite the first side, an acoustically effective first microperforated sheet arranged on the first side of the absorber layer, an acoustically effective second microperforated sheet arranged on the first side of the absorber layer.
 2. The shielding element of claim 1, wherein the first microperforated sheet and the second microperforated sheet are immediately adjacent to one another.
 3. The shielding element of claim 2, wherein the second microperforated sheet is immediately adjacent to the absorber layer.
 4. The shielding element of claim 1, wherein the layered construction further has a third microperforated sheet arranged on the second side of the absorber layer.
 5. The shielding element of claim 1, wherein the first side of the absorber layer faces away from the support plate.
 6. The shielding element of claim 1, wherein the first microperforated sheet is a heat sealing sheet.
 7. The shielding element of claim 4, comprising a sequence of layers in the following order: the support plate, the third microperforated sheet, the absorber layer, the second microperforated sheet and the first microperforated sheet.
 8. The shielding element of claim 7, wherein the first microperforated sheet is a heat sealing sheet.
 9. The shielding element of claim 1, wherein the first side of the absorber layer faces the support plate.
 10. The shielding element of claim 1, wherein the first microperforated sheet has a thickness within a range of approximately 20 μm to approximately 150 μm.
 11. The shielding element of claim 1, wherein the first microperforated sheet has a thickness within a range of approximately 40 μm to approximately 60 μm.
 12. The shielding element of claim 1, wherein the second microperforated sheet has a thickness within a range of approximately 20 μm to approximately 150 μm.
 13. The shielding element of claim 1, wherein the second microperforated sheet has a thickness within a range of approximately 40 μm to approximately 60 μm.
 14. The shielding element of claim 1, wherein the first microperforated sheet has a perforation with holes which have an individual diameter within a range of approximately 50 μm to approximately 200 μm.
 15. The shielding element of claim 1, wherein the first microperforated sheet has a perforation with holes which have an individual diameter within a range of approximately 80 μm to approximately 100 μm.
 16. The shielding element of claim 1, wherein the second microperforated sheet has a perforation with holes which have an individual diameter within a range of approximately 50 μm to approximately 200 μm.
 17. The shielding element of claim 1, wherein the second microperforated sheet has a perforation with holes which have an individual diameter within a range of approximately 80 μm to approximately 100 μm.
 18. The shielding element of claim 1, wherein the first microperforated sheet has a perforation with holes which have a surface covering within a range of approximately 20 to approximately 80 holes per cm².
 19. The shielding element of claim 1, wherein the first microperforated sheet has a perforation with holes which have a surface covering within a range of 40 to approximately 60 holes per cm².
 20. The shielding element of claim 1, wherein the second microperforated sheet has a perforation with holes which have a surface covering within a range of approximately 20 to approximately 80 holes per cm².
 21. The shielding element of claim 1, wherein the second microperforated sheet has a perforation with holes which have a surface covering within a range of 40 to approximately 60 holes per cm².
 22. A sound-absorbing shielding element, comprising a layered construction having: a support plate, an acoustically effective porous absorber layer, an acoustically effective first microperforated sheet arranged on the first side of the absorber layer, an acoustically effective second microperforated sheet arranged between the absorber layer and the first microperforated sheet, and an acoustically effectice third microperforated sheet arranged between the support plate and the absorber layer.
 23. The shielding element of claim 22, wherein the second microperforated sheet is immediately adjacent to the first microperforated sheet and to the absorber layer.
 24. The shielding element of claim 23, wherein the first microperforated sheet is a heat sealing sheet made of aluminium. 